Experiences with the BIRD magnetic coil system for wheel desaturation, satellite rate damping and attitude control - the concept of virtual wheel systems

Kurzfassung

The small LEO satellite BIRD (Bi Spectral Infrared Detection) was launched October 2001. It was mainly developed as an infrared detection and technology demonstrator with a hard “design to cost philosophy”. One point was a short nominal life time of one year in space. It influenced several aspects of satellite design and selection of components. But BIRD operated without any problem for two years before serious problems started. In February 2003 BIRD lost the one and only gyro system (Honeywell, HG1700 AE09) Wrong gyro output led to a loss of 3 from 4 reaction wheels. Only the magnetic coil system kept the satellite in a safe and stable orientation and guaranteed the survival of the satellite for 6 month without any software change on board. In August 2004 changed software was loaded in order to improve the attitude control and to get a better sun orientation. It was successful, even Earth observation became again possible as it was demonstrated by some data takes around the world.